1. Field of the Invention
The present invention relates to a gate valve which is suitable for use in a pendulum valve, a direct acting valve, a door valve, or the like, which slidably operates a valve plate in addition to an operation of opening and closing a flow passage using the valve plate.
Particularly, the present invention relates to a gate valve which separates (closes) flow passage communicating two spaces in which the vacuum degrees thereof (including atmospheric pressure) are different from each other in a vacuum apparatus or the like and which releases this separated state (communicates the two spaces).
2. Background Art
Gate valves are provided in a vacuum apparatus or the like, and the gate valves separate two spaces in which the vacuum degrees thereof are different from each other such as between a chamber and pipes, between pipes, between a pipe and a pump, or the like; and the gate valves communicate the two spaces.
As such a gate valve, various valves are known.
For example, a structure is known in which a valve plate is inserted into a valve opening-closing position of a flow passage by sliding a valve plate, furthermore, the flow passage is separated (valve closing operation) or two flow passages are communicated by operating the aforementioned valve plate (valve opening operation) by operating this valve plate. Additionally, the valve plate is moved to a safety position located in a valve box from the flow passage by sliding the valve plate.
As a valve having such a structure, a pendulum valve, a direct acting valve, a door valve, or the like is known.
A direct acting gate valve has a constitution in which a valve plate is disposed in a hollow portion of a valve box. A first opening portion and a second opening portion constituting a flow passage are formed at the valve box. The valve plate is securely fixed to a valve rod (support body).
In this structure, the aforementioned valve plate is inserted into the valve opening-closing position of the opening portion (flow passage) by moving straight the aforementioned valve rod in the longitudinal direction thereof, or the aforementioned valve plate is moved to the safety position at which the opening portion is not formed.
As a conventional direct acting gate valve, a gate valve is known which is provided with a valving element that is constituted of two of a first valve plate and a second valve plate which are connected to each other with bellows interposed therebetween, an actuator be disposed at the center portion of the valve plate between these two valve plates, and a valve box at which an opening portion constituting the flow passage is formed.
In this gate valve, the flow passage is closed due to the first valve plate coming in contact with and pressing onto the peripheral inner surface of the opening portion of the valve box by operating the actuator, or the flow passage is released due to separating the first valve plate from the inner surface of the aforementioned valve box by operating the actuator (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2002-181205).
Additionally, a pendulum gate valve has a constitution in which a valve box having a hollow portion, a support body, and a valving element (a valve plate in the case of the structure in which a seal ring plate is provided at an opening portion) which is securely fixed to this support body. In the valve box, a first opening portion and a second opening portion constituting a flow passage are formed. The support body is securely fixed to a rotation shaft in the hollow portion and is expanded in a direction parallel to the plane perpendicular to the rotation shaft.
In this gate valve, the aforementioned valving element is turned by rotating the aforementioned rotation shaft, therefore, the above-described valving element is inserted into the valve opening-closing position of the opening portion (flow passage) or the above-described valving element is moved to the safety position at which the opening portion is not formed.
As a conventional pendulum gate valve, a constitution is known in which a valve plate that is capable of rotating around a rotation shaft in a hollow portion of a housing, a slidable seal ring plate that is disposed at an opening portion of the housing, and an actuator allowing the aforementioned seal ring plate to slide on a flange formed integrally with the housing are provided.
In this gate valve, the flow passage is closed due to the aforementioned seal ring plate coming in contact with and pressing onto the aforementioned valve plate, or the flow passage is released by separating the aforementioned seal ring plate from the aforementioned valve plate (for example, refer to Japanese Patent No. 3655715).
The actuator provided in this pendulum gate valve has a structure in which a bolt, a ring-shaped chamber (cylinder), a piston, and a spring are arranged in series in the sliding direction of the seal ring plate.
For this reason, when the flow passage is being closed, the restorative force generated in the spring is transmitted to the seal ring plate through the piston, the cylinder, and the bolt.
Additionally, a door gate valve has a constitution in which a valve box having a hollow portion, a support body, and a valving element which is securely fixed to this support body. In the valve box, a first opening portion and a second opening portion constituting a flow passage are formed. The support body is securely fixed to a valve shaft and is expanded in a direction parallel to the plane including the valve shaft.
In this gate valve, the above-described valving element is rotated by rotating the aforementioned valve shaft, the above-described valving element is inserted into the valve opening-closing position of the opening portion (flow passage) or, the above-described valving element is moved to the safety position which is substantially perpendicular to the opening portion.
In the foregoing gate valve, for the requirement of making the overall structure of the gate valve compact, it is necessary to simplify the structure of the valving element and to ensure the reliability of separating operation.
However, in conventional valves as described above, since the actuator is disposed at the center portion of the valve plate, a high level of rigidity in the valve plate is required for transmitting a sufficient pressing force to the surface of the valve plate which seals a space as a practical matter.
If the rigidity in the valve plate is insufficient, there are problems in that it is not possible to reliably separate spaces and a high level of reliability cannot be obtained.
Furthermore, in the above-described conventional valves, a structure connecting two valve plates is adopted.
Since this connection structure and the actuator are individual components, there is a problem in that the structure of the valving element becomes complicated.
Moreover, in a large-diameter valve, a cylinder which produces great power is necessary for resisting the back pressure, and there is a problem in that the valving element becomes larger.
Additionally, in the above-described conventional pendulum gate valve, an actuator allowing the seal ring to slide is provided at a flange, and this actuator, a ring-shaped cylinder, and a spring are arranged in series.
Consequently, the surface of the valve plate which actually seals a space is positioned inside of the actuator, this surface is displaced from the position of the actuator, furthermore, a pressing force by the spring (restorative force of spring) is transmitted to this surface through the piston, the cylinder, and the bolt.
For this reason, if this pressing force is insufficient, there are problems in that it is not possible to reliably separate spaces and a high level of reliability cannot be obtained.
In addition, in order to resist the back pressure in a large-diameter valve or to apply a valve plate, a seal ring plate, a flange having a particular kind of configuration, it is necessary to arrange a plurality of actuator components excluding a cylinder, and there is a problem in that the constitution of the gate valve becomes complicated.